Each year over one million Cub Scouts in over 47,000 Cub Scout Packs participate in a very special event: The Pinewood Derby®. Initiated in 1953, the program adopted by The Boy Scouts of America® has become an enormous success. Cub Scouts who win local Den and Pack races move on to district finals. The popular event has expanded to other youth groups including the Girl Scouts. International programs have been established.
Children, 7 through 10 years of age, along with a parent or sponsor, create a race car from a block of wood, four axles and a set of plastic wheels. The Derby car, with the force of gravity, runs down an inclined track over a central guide rail to the finish line. Adhering to basic Pack rules and principles of design, weight distribution, wheel and axle preparation, and alignment, the Cub Scout along with his parent attempts to build a winning car.
The emphasis in this team effort is to promote the parent/child relationship and to provide a learning experience with the active participation of the Cub Scout. Techniques to reduce wheel and axle friction, the enemy of speed, often involve power tools and machine shop equipment including a drill press or machine shop lathe which the Cub Scout cannot safely use. This truing of the wheels and axles is an important objective in building the race car. It has been recognized as the single most important principle to attaining optimal derby car speed.
Structure defines function and function defines performance. Structural defects produced during the manufacture of derby car wheels and axles have been well described. The plastic wheels are generally manufactured using a mold injection process that can lead to defects in the wheel circumference, wheel tread, central axle hole and hub. The wheel may not be round to the central axle hole. It may have uneven treads containing divots and inner wheel sidewall rim profiles that are irregular. Under these conditions friction is increased as the rotating wheel hobbles, vibrates, veers and rubs against the guide rail. Moreover, wheel axle manufacturing imperfections contributing to friction include so-called gussets inside the head surface and burrs on the axle shaft.
There has been a longstanding need for a device which would enable a child to remove imperfections in a way that, ideally, reduces vibration and friction by providing interactive wheel and axle surfaces that are horizontal or perpendicular to the axis of rotation. A flat wheel tread horizontal to the axis of rotation provides for a wheel central axle hole rotating horizontal to axle alignment and a flat tread configuration on the race track that minimizes friction. The horizontal tread configuration reduces outer and inner rim circumference size discrepancies which, if present, can transmit frictional torque forces to the wheel central axle hole on axle interface. Wheels of different diameter can transmit frictional torque forces to the wheel central axle hole, axle interface. The inner rim sidewall, if not revolving throughout its entire circumference in a plane perpendicular to the axis of rotation, could cause a wheel in contact with the rail guide to oscillate on the axle.
A structured workstation device was conceived to address these concerns and the need to enable Cub Scout participation in the preparation and the truing of wheels and axles. Emphasis in its design was to provide a unique opportunity for the Cub Scout to create:    a. four wheels uniformly round to the central axle hole.    b. four wheels with identical diameter and circumference.    c. wheel treads flat and horizontal to the axis of rotation.    d. wheel inner sidewall rims with flat profiles at 90 degrees to the axle throughout a complete rotation of the inner sidewall of the wheel.    e. an axle head free of defects with the inner surface at 90 degrees to the axle shaft throughout the complete circumference of the axle head.    f. an axle shaft free of burrs, horizontal to the axis of rotation.
The device provides for slidable platform embodiments with predetermined planes to which abrasive materials and implements can be applied, directing a mechanical energy toward the task of truing model car wheels and axles at 90 degrees and 180 degrees to the axis of rotation. For the Cub Scout who does not have access to complex machine shop equipment, it equals the playing field. Moreover, the workstation embodiment has been reduced to practice. A prototype has been built, tested and has performed with accuracy. The marketing potential is formidable.